The conventional laser optical resonator consists of two spherical mirrors or a spherical mirror and a plane mirror with dimensions about one hundred thousand times of that of the wavelength. The microwave quasi-optical resonator also adopts the same structure and principle. However, because the wavelength is much greater than the optical wavelength, the dimensions of the chamber are only a dozen or a few dozen times the wavelength. Hence it is called a quasi-optical resonator.
Heating by microwave, compared with radiation heating by a conventional high temperature furnace, has many advantages, such as instant penetration, fast heating speed, short action time and saving of energy. Hence it is gradually becoming accepted and increasingly popular. The present microwave action chambers are made in various forms. But the main body of the system generally adopts a closed resonator. Material is heated in an electromagnetic wave field in a microwave mode.
The present closed resonator has three limitations when in use: 1. the dimension of the material is limited by the size of the resonator; 2. the electromagnetic wave field in the microwave mode is not uniform, which results in uneven treatment of the material; and 3. the field is distributed over the entire chamber, which limits the heating speed.
Because of the aforesaid limitations, the conventional closed resonator cannot meet the material treatment requirements of new material developments and technologies. For instance, electronic textile that contains deformable electronic modules is one focus of future technologies. Such products have a large area, and the modules have materials withstanding different-temperature material treatment that cannot be supported by the manufacturing process proceeding at the same temperature. Hence a strong absorption layer that can be heated quickly and locally is required in the development of a new technique to bond a functional layer and the substrate material of a lower melting point. The present closed microwave resonator and the conventional thermal radiation heating chamber cannot meet the requirements of those new materials and manufacturing processes. Therefore a new action chamber has to be developed to meet those requirements.